In a train control system utilizing conventional inter-train communications, a preceding train transmits to a following train a transmission signal including a train ID (identification data: a number or the like for distinguishing a train) and a train location, an onboard device of the following train reads out the received train ID and train location of the preceding train, and the running speed of the following train is controlled based on a current location and a train speed of the following train that are sensed or calculated similarly to the preceding train (for example, refer to Patent Document 1).
Meanwhile, as an existing signal system that controls trains without using the inter-train communications, there is an Automatic Train Control (ATC) signal system in which a rail track is divided into track sections, and trains are detected in each of the track sections, whereby, based on the detected information, a transmission signal including information for controlling that only one train can enter into each of the track sections is transmitted by the rail track as a transmission medium on an every track section basis (for example, refer to Non-Patent Document 1).
In addition, as another existing signal system that controls trains without using the inter-train communications, there is an automatic train control system by radio in which, without dividing a rail track into track sections, individual trains measure locations of the trains themselves and transmit them to a ground-based device, whereby the ground-based device determines a stop location of a following train based on a train location of a preceding train, and the ground-based device transmits using a radio device a transmission signal by this existing signal system to the following train (for example, refer to Patent Document 2).
In the train control system utilizing the inter-train communications described above, trains can be made running closer to each other in comparison with the existing signal systems that control the trains without using the inter-train communications. Namely, in comparison with the train control by the ATC signal system in which only one train can enter into each of the track sections, the following train runs based on the train location of the preceding train, so that a closer running can be achieved.
In addition, in comparison with the train control using an automatic train control system by radio in which the location information of a preceding train is transmitted to a following train once by means of the ground-based device, a delay time for receiving information of the train location by the following train can be shortened, so that a closer running can be achieved.